Controllable coolant pump

ABSTRACT

A controllable coolant pump for a coolant circuit of an internal combustion engine, the coolant pump including a hollow bearing shaft which is supported in a bearing sleeve, carries a drive wheel at one end, and is permanently connected at its opposite end to an impeller, the impeller having a stop surface at the end face thereof; the space between the stop surface and the impeller forming the pumping cross section for a coolant, and a piston that can be axially displaced by an actuation unit being disposed in the hollow bearing shaft and provided at its outer end with a guide plate having a collar facing the impeller for completely or partially closing the pumping cross section in accordance with the position of the piston. The actuation unit has a release lever which can be pivoted by an electromechanical actuating element about an axis of rotation, thus allowing axial positioning of the piston.

The present invention relates to a controllable coolant pump for a coolant circuit of an internal combustion engine. The coolant pump has a hollow bearing shaft which is supported in a bearing sleeve, carries a drive wheel at one end, and is permanently connected at its opposite end to an impeller, the impeller having a stop surface at the end face thereof. The space between the stop surface and the impeller forms the pumping cross section for a coolant. A piston that can be axially displaced by an actuation unit is disposed in the hollow bearing shaft and provided at its outer end with a guide plate having a collar for completely or partially closing the pumping cross section in accordance with the position of the piston.

BACKGROUND

Water-cooled engines have become predominant in the field of internal combustion engines. In such engines, cooling water is pumped by a coolant pump in a closed loop through cooling passages in the region of the cylinders in order to cool the internal combustion engine, and is then conveyed to an air/water radiator, where the heated water is cooled down by the relative wind generated by the motion of the vehicle. The pump required to circulate the cooling water is typically connected by a belt to a pulley of the crankshaft of the internal combustion engine.

Since the coolant pump is directly coupled to the crankshaft in this way, the rotational speed of the pump is dependent on the rotational speed of the internal combustion engine. As a result, in the high speed range of the internal combustion engine, the pump delivers a correspondingly high flow rate, which exceeds that required for cooling. However, during cold starting of the internal combustion engine, the problem arises that coolant is immediately circulated through the cooling passages, thereby hindering the heating of the combustion chambers and delaying the attainment of an optimum operating temperature.

A controllable coolant pump of the aforementioned type is known from German Patent Application DE 2008 046 424 A1. In this coolant pump, a guide plate having a contour corresponding to the impeller is disposed between the impeller and a stop surface, the guide plate being guided by axial webs connecting the impeller and the stop surface, and being axially displaceable by an actuation unit by means of a piston placed within the hollow shaft.

The guide plate is provided at its outer edge with a collar by which it may cover an annular channel of a pump housing depending on its position between the impeller and the stop surface. Thus, the annular channel can be fully or partially covered, so that no cooling liquid is pumped through the cooling passages. The axial positioning of the piston is accomplished by means of a magnet. While this conventional coolant pump has proven suitable, there is a need for a coolant pump with improved controllability.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a controllable coolant pump whose controllability is improved, in particular during cold starting.

In a controllable coolant pump of the type mentioned at the outset, the present invention provides that the actuation unit has a release lever which can be pivoted by an electromechanical actuating element about an axis of rotation, thus allowing axial positioning of the piston.

In accordance with the present invention, the controllability of the coolant pump can be significantly improved by providing a release lever which is coupled, connected, or connectable to the electromechanical actuating element as an actuator and to the piston. The release lever may have a first lever arm and a second lever and is pivotable about an axis of rotation. Thus, actuation (i.e., displacement) of the piston, and thus control of the flow rate, can be accomplished in a simple manner in that the actuating element acts on a lever arm of the release lever, thereby pivoting the release lever about the axis of rotation. In being pivoted, the other lever arm displaces the piston, thereby adjusting or varying the pumping cross section for the coolant. Alternatively, the lever may have only one lever arm and be pivotable about an end of the lever.

In the coolant pump of the present invention, it is preferred for the release lever to be pivoted at the bearing sleeve. Preferably, the release lever may be stationarily arranged at the bearing sleeve such that it is pivotable about its attachment point. The attachment point is preferably designed as a bearing point. With regard to the attachment of the release lever, basically two positions at the bearing sleeve are possible. The release lever may either be attached to the bearing sleeve near the actuation unit, or alternatively, the release lever may be attached to the bearing sleeve at the opposite side thereof at a position remote from the actuation unit.

Particularly high functional reliability is achieved for the coolant pump of the present invention when an axial bearing is provided between the second lever arm of the release lever and the piston. The axial bearing serves for rotational isolation of the release lever and the piston. Preferably, the axial bearing includes two disks having rolling elements disposed therebetween. In the simplest case, the rolling elements may be replaced with an additional disk or the like. One disk of the axial bearing contacts the second lever arm of the release lever, while the other disk of the roller bearing contacts the piston, which may have a transverse pin or the like. When the piston rotates, the rotation is accommodated by the disk of the axial bearing that is connected to the piston in that this disk is also set in rotation. In the process, the rolling elements between the two disks of the axial bearing are set in rotation, but the disk of the axial bearing that is associated with the release lever is not set in rotation. In this way, the desired rotational isolation is achieved.

In a refined embodiment of the present invention, the second lever arm of the release lever may have two spaced-apart end portions engaging the axial bearing, in particular a disk of the axial bearing. The second lever arm of the release lever may be forked and have an enlarged region between the end portions of the fork. The drive shaft and the piston are disposed inside the sleeve.

It is also within the scope of the present invention that the electromechanical actuating element may have an axially displaceable lead screw acting upon the release lever. The use of a lead screw allows for particularly precise displacement of the piston, thus enabling accurate control of the pumping cross section for the coolant.

It is particularly preferred for the lead screw to be coupled to a lead screw nut driven by an electric motor. The electric motor and the lead screw nut are arranged in fixed positions. Rotation of the drive shaft of the electric motor rotates the lead screw nut, thereby axially displacing the lead screw.

The electric motor of the coolant pump of the present invention may have a pinion meshing with the lead screw nut, making it possible to change the rotational speed between electric motor and the lead screw.

A particularly fail-safe variant of the controllable coolant pump is obtained if it includes a second electromechanical actuating element for pivoting the release lever, the second electromechanical actuating element being independent of the first electromechanical actuating element. The second electromechanical actuating element may either be actuated as an alternative to actuation of the first electromechanical actuating element or used when the first electromechanical actuating element has a defect.

To enable highly accurate positioning of the piston, and thus accurate adjustment of the pumping cross section, the coolant pump of the present invention may include a sensor for detecting the axial position of the piston. Preferably, the sensor is adapted for non-contact position detection.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are illustrated in the drawings and described in more detail below. In the drawings,

FIG. 1 is a cross-sectional view of a conventional controllable coolant pump;

FIG. 2 is a cross-sectional view of a first exemplary embodiment of a coolant pump according to the present invention;

FIG. 3 shows the coolant pump of FIG. 2 with the piston extended;

FIG. 4 is a transverse cross-sectional view of the coolant pump shown in FIGS. 2 and 3;

FIG. 5 shows a second exemplary embodiment of a coolant pump according to the present invention;

FIG. 6 shows the coolant pump of FIG. 5 with the piston in the extended position;

FIG. 7 is a transverse cross-sectional view of the coolant pump shown in FIGS. 5 and 6;

FIG. 8 is a cross-sectional view of a third exemplary embodiment of a coolant pump;

FIG. 9 shows the coolant pump of FIG. 8 with the piston in the extended position; and

FIG. 10 illustrates another operating condition of the coolant pump shown in FIGS. 8 and 9.

DETAILED DESCRIPTION

The design and operation of a controllable coolant pump is described with reference to FIG. 1. FIG. 1 is a cross-sectional view showing a conventional coolant pump 1 including a bearing shaft 3 which is supported in a pump housing 2, carries a drive wheel 4 at one end, and is permanently connected at its opposite end to an impeller 5. Impeller 5 has a stop surface 6 at the end face thereof. The space between stop surface 6 and impeller 5 forms the pumping cross section for a coolant, in particular cooling water. A piston 7 that can be axially displaced by an actuation unit (not shown) is disposed in hollow bearing shaft 3 and provided at its outer end with a guide plate 8 having a collar 9 for completely or partially closing the pumping cross section in accordance with the position of piston 7.

When piston 7 is in the position shown in FIG. 1, the pumping cross section between arrows 10 is cleared. When piston 7 is displaced in a direction toward stop surface 6 by an electromechanical actuating element, the pumping cross section is reduced or completely closed. This allows control of the coolant flow pumped into cooling passages of an internal combustion engine.

Upon starting of the internal combustion engine, the drive wheel 4 coupled by a belt to the crankshaft is set in rotation. Accordingly, bearing shaft 3 rotates impeller 5, thereby pumping coolant. However, during cold starting, pumping of coolant it is initially not desired, so that piston 7 is displaced in a direction toward impeller 5, thereby closing the pumping cross section. In this condition, no coolant is pumped, which speeds up the heating of the engine. During normal operation, the pumping cross section is partially or completely cleared, so that the coolant is pumped through cooling passages of the internal combustion engine, thus cooling the engine.

The following exemplary embodiments of coolant pumps are in principle designed similar to the one shown in FIG. 1. However, for the sake of clarity, individual components which are irrelevant to the understanding of the present invention are not shown in the respective drawings. In particular, the drive wheel, the impeller, and the guide plate have been omitted for the sake of simplicity.

FIG. 2 shows a coolant pump 11 in cross-sectional view. A hollow bearing shaft 12 receives therein an axially displaceable piston 13. Bearing shaft 12 is supported by roller bearings 14 in a bearing sleeve 15.

Coolant pump 11 includes a release lever 16 which is pivotable about an axis of rotation 17. A first lever arm 18 of release lever 16 can be pivoted by an electromechanical actuating element. The electromechanical actuating element includes an electric motor 19 whose drive shaft 20 includes pinion 21 meshing with a lead screw nut 22. Rotation of lead screw nut 22 causes a lead screw 23 to be axially displaced, one end of lead screw 23 acting upon first lever arm 18 of release lever 16, thereby pivoting release lever 16 about its axis of rotation 17.

A second lever arm 24 of release lever 16 acts upon an axial bearing 25. Second lever arm 24 and axial bearing 25 are located within bearing sleeve 15, whereas first lever arm 18 of release lever 16 is located outside of bearing sleeve 15. In the region of axis of rotation 17, bearing sleeve 15 has an opening penetrated by release lever 16.

Axial bearing 25 includes a first disk 26, rolling elements 27, and a second disk 28 which is connected to a transverse pin 29 extending through piston 13 in a transverse direction. Thus, first disk 26 of axial bearing 25 is in contact with release lever 16, while second disk 28 of axial bearing 25 is in contact with transverse pin 29, and thus with piston 13. In the simplest case, rolling elements 27 may be replaced with a disk.

FIG. 2 shows the coolant pump with the pumping cross section open and cleared, so that the coolant is pumped into cooling passages. If the pumping cross section is to be reduced or closed, then the electromechanical actuating element is operated. Drive shaft 20 of electric motor 19 rotates pinion 21, thereby rotating lead screw nut 22. Accordingly, lead screw 23 is axially displaced (to the left in the view of FIG. 2), thereby pivoting release lever 16 from the position shown in FIG. 2 to the position shown in FIG. 3. Release lever 16 pivots about axis of rotation 17. Second lever arm 24 of release lever 16 engages disk 26 of the axial bearing and pushes it to the right in the view of FIG. 3. Since second disk 28 of axial bearing 25 is coupled to piston 13 by transverse pin 29, piston 13 is axially displaced to the right in the view of FIG. 3. Since a guide plate (not shown) is disposed at the end of the piston, the pumping cross section is reduced or closed.

FIG. 4 shows coolant pump 11 in transverse cross-sectional view. It can be seen that the schematically depicted second lever arm 24 of release lever 16 is forked and in contact with disk 26.

FIG. 5 shows a second exemplary embodiment of a coolant pump in cross-sectional view. The design and function of coolant pump 30 shown in FIG. 5 basically corresponds to that of the first exemplary embodiment and, therefore, corresponding components and their operation are not described again here.

In contrast to the preceding exemplary embodiment, axis of rotation 31 of release lever 32 is located on bearing sleeve 15 at a position remote from the actuating element. Release lever 32 is hinged at a point opposite the actuating element.

FIG. 7 shows coolant pump 30 in a transverse cross-sectional view, in which it can be seen that release lever 32 is forked and has a central portion of enlarged diameter, and that bearing shaft 12 and piston 13 are surrounded by release lever 32.

In order to adjust the pumping cross section, electric motor 19 is energized, thereby displacing lead screw 23 (to the right in the view of FIG. 5). Lead screw 23 acts upon release lever 32, pivoting it clockwise about its axis of rotation 31. A central portion 33 of lever 32, which is convexly curved toward axial bearing 25, engages axial bearing 25 and displaces it to the right in the view of FIG. 5. Since axial bearing 25 is coupled to piston 13, the piston is moved axially out of bearing shaft 12.

FIG. 6 shows coolant pump 30 after it has been operated by the actuation unit. Release lever 32 has be displaced maximally by lead screw 23, displacing axial bearing 25 within bearing sleeve 15 axially to the right. Further displacement is prevented by transverse pin 29. When piston 13 is in this position, the pumping cross section is closed, so that no coolant is pumped.

FIGS. 8, 9 and 10 show a third exemplary embodiment of a coolant pump. Coolant pump 34 is similar in basic design to the exemplary embodiment illustrated in FIGS. 5 through 7 and, therefore, corresponding components are not described in detail again here.

Release lever 35 is pivotable about an axis of rotation 36, which is located outside of bearing sleeve 15 at the end of lead screw 37

FIG. 8 shows cooling pump 34 in a normal position. Analogously to the preceding exemplary embodiment, displacement of piston 13 is accomplished by means of electric motor 19 and lead screw 23. When lead screw 23 is axially moved, release lever 35 displaces piston 13 via axial bearing 25 in the axial direction (to the right in the view of FIG. 8), thereby reducing or possibly closing the pumping cross section.

FIG. 9 shows coolant pump 34 with piston 13 fully extended, with lead screw 23, release lever 35, and piston 13 maximally moved or extended respectively. In this condition, no coolant can be pumped. Therefore, if the actuation unit including the electric motor, the pinion, the lead screw nut and lead screw 23 fails, there is a risk of the internal combustion engine overheating and being damaged. Therefore, in order to increase fault tolerance, a second actuation unit is provided which is identical in design to the first actuation unit. Accordingly, the second actuation unit includes an electric motor 38 which drives lead screw 37 via a pinion and a lead screw nut.

A potential failure of the first actuation unit may be detected, for example, by resistance measurement. The position of a lead screw can be detected by a position sensor. Alternatively or additionally, piston 13 may also have a position sensor associated therewith.

If the first actuation unit is detected to have failed, return to the initial state may be accomplished by the second actuation unit. This state is shown in FIG. 10. It can be seen there that the position of the lead screw 23 of the first actuation unit has not changed from that in the state illustrated in FIG. 9. In contrast, lead screw 37 has been moved by electric motor 38 in the axial direction (to the left in the view of FIG. 10). Because of this, the end of release lever 35 forming axis of rotation 36 has been displaced to the left, resulting in a displacement of axial bearing 25 and piston 13 to the left, thereby clearing the pumping cross section. The second actuation unit including electric motor 38 and lead screw 37 can take over the control of the coolant pump in the event of failure of the first actuation unit.

LIST OF REFERENCE NUMERALS

-   1 coolant pump -   2 pump housing -   3 bearing shaft -   4 drive wheel -   5 impeller -   6 stop surface -   7 piston -   8 guide plate -   9 collar -   10 arrow -   11 coolant pump -   12 bearing shaft -   13 piston -   14 roller bearing -   15 bearing sleeve -   16 release lever -   17 axis of rotation -   18 first lever arm -   19 electric motor -   20 drive shaft -   21 pinion -   22 lead screw nut -   23 lead screw -   24 second lever arm -   25 axial bearing -   26 disk -   27 rolling elements -   28 disk -   29 transverse pin -   30 coolant pump -   31 axis of rotation -   32 release lever -   33 convex portion -   34 coolant pump -   35 release lever -   36 axis of rotation -   37 lead screw -   38 electric motor 

1-10. (canceled)
 11. A controllable coolant pump for a coolant circuit of an internal combustion engine, the coolant pump comprising: a hollow bearing shaft supported in a bearing sleeve and carrying a drive wheel at one end, the hollow bearing shaft being permanently connected at an opposite end to an impeller, the impeller having a stop surface at the end face thereof; the space between the stop surface and the impeller forming the pumping cross section for a coolant; and a piston axially displaceable by an actuation unit disposed in the hollow bearing shaft and provided at an outer end with a guide plate having a collar facing the impeller for completely or partially closing the pumping cross section in accordance with the position of the piston, the actuation unit having a release lever pivotable by an electromechanical actuating element about an axis of rotation to permit axial positioning of the piston.
 12. The controllable coolant pump as recited in claim 11 wherein the release lever is pivoted at the bearing sleeve.
 13. The controllable coolant pump as recited in claim 11 wherein the release lever has a first lever arm and a second lever arm, and an axial bearing is provided between the second lever arm of the release lever and the piston.
 14. The controllable coolant pump as recited in claim 13 wherein the axial bearing includes two disks having rolling elements disposed therebetween.
 15. The controllable coolant pump as recited in claim 13 wherein the second lever arm of the release lever has two spaced-apart end portions engaging the axial bearing.
 16. The controllable coolant pump as recited in claim 15 wherein the two-spaced-apart end sections engage a disk of the axial bearing.
 17. The controllable coolant pump as recited in claim 11 wherein the electromechanical actuating element has an axially displaceable lead screw acting upon the release lever.
 18. The controllable coolant pump as recited in claim 17 wherein the lead screw is coupled to a lead screw nut driven by an electric motor.
 19. The controllable coolant pump as recited in claim 18 wherein the electric motor has a pinion meshing with the lead screw nut.
 20. The controllable coolant pump as recited in claim 19 wherein the coolant pump includes a second electromechanical actuating element for pivoting the release lever, the second electromechanical actuating element being independent of the first electromechanical actuating element.
 21. The controllable coolant pump as recited in claim 11 further comprising a sensor for detecting the axial position of the piston. 